Preparation and properties of UV-curable polyurethane methacrylate cationomers and their use as adhesives

Cationomeric polyurethanes (containing methacrylic functionality) were prep ared from a diisocyanate [toluene diisocyanate (TDI), hexamethylene diisocy anate (HDI), or isophorone diisocyanate (IPDI)], polyethylene glycol (PEG 2 00, PEG 400, or PEG 1000), 2-hydroxyethyl methacrylate (HEMA), N-methyldiet hanolamine (N-MDEA), and dimethyl sulfate (DMS), using dibutyltin dilaurate (DBTDL) as a catalyst. The ultraviolet (UV) curable aqueous cationomeric e mulsions were then made with these reactive polyurethane oligomers (having hydrophilic groups), water, and photoinitiator [1-(4-isopropylphenyl)-2-hyd roxy-2-methyl propane-1-one]. The effects of PEG chain length and different diisocyanates on properties of the emulsions were studied. The effect of c oncentration of cationomers on the thermal stability of these systems was a lso studied. These emulsion systems were evaluated as adhesives before and after curing under UV light. With decrease in PEC molecular weight, the gla ss transition temperature of the polymers increased and the storage modulus , tensile strength, and peel strength also increased. but the percentage of elongation decreased, Polymer containing TDI was found to have the highest glass transition temperature, storage modulus, peel strength, and tensile strength when compared to the polymer containing HDI or IPDI.